Patent Literature (PTL) 1 discloses a technique for improving the availability of an information system. Specifically, first and second storage apparatuses, coupled to a host computer, have set therein a remote copy pair for copying data of a first volume in the first storage apparatus to a second volume in the second storage apparatus, and associate a third volume in a third storage apparatus with the remote copy pair. When an I/O request to the first volume ends in an error, the host computer sends the second storage apparatus an I/O request to the second volume. When the first or second storage apparatus detects a failure in its partner first or second storage apparatus or detects a coupling failure between the first and the second storage apparatuses, the first or second storage apparatus stores in the third volume a failure information flag indicating the detection of the failure.